Question:
What are the less obvious signs of stress in a fish? Diseases, death,
changes in activity level, being less colorful, not eating, rubbing
against things, labored breathing are the readily apparent ones, but if a
fish was showing none of these signs, would there be any other
indicators?
Answer:
That's already a pretty complete list you've provided. You are going to
make us work to give more symptoms.
i) Reflection, viewed at an angle, are their scales as reflective (or
matt) as their sibling's
ii) Transparency of the rays, especially the caudal fin. During
prolonged stress, the fins may develop a slight transparency (loss of
opaqueness ?) starting at the base moving towards the tips of the fin.
iii) Fin clamping
iv) Cloudiness over the eyes.
v) Colour of the gills.
vi) Different swimming depth in tank as compared to siblings.
vii) Trouble maintaining orientation.
So if a fish isn't showing any symptoms from either list, is it safe to
assume it's probably fine?
On one hand, susceptibility to anything which is not the ideal salinity,
or ideal pH or gH, I think has been overestimated. Healthy uncrowded
fish will often acclimate very well to stable conditions outside the
ideal, and many fish are quite capable of regulating their internal
salinity even moving from fresh to marine environments. A few teaspoons
of salt are hardly an extreme condition. I wonder of someone could
provide a link to a salinity concentration table showing teaspoons per
gallon, and also where brackish and marine conditions are typically
considered to start & end.
On the other hand, internal stress such as from internal bacterial
contagions, may not show any symptoms until it has progressed beyond
practical treatments (ie: types of Dropsy). I would refer to the
salinity concentration tables to see where you are, but I suspect, from
your description that you are fine unless you have fish which have known
sensitivities to salt (and even those may surprise you if all other
conditions are good).
